Actually, there are a myriad of laws on the books that govern what elected officials are allowed to take from others, especially lobbyists. There are even watchdog groups to cry foul when some of them do things that are on the edge of legality, ask Trent Lott or Maxine Waters, or Charlie Wrangel.. Sometimes they even get called before the ethics committee.
I would be in favor of enforcement of existing law that had more teeth and more bitter consequences, but then you run the risk of having a one-party rule where the members of the other party get unfairly railroaded... The system we have is certainly imperfect, but not as fundamentally broken as some claim.